Staunch conservative allies of President Trump erupted in anger and incredulity late Wednesday after Democrats announced the president had agreed to pursue a legislative deal that would protect thousands of young undocumented immigrants from deportation but not secure Trump's signature campaign promise: building a massive wall along the U.S.-Mexico border.

As midnight neared, thousands of social media accounts came alive as elected officials and activists on the right dashed off tweets and posts to share their shock.

And in between those posts, there was a flurry of fuming calls and text messages â€” a blaring political fire alarm among Trump's diehard supporters.

"The reality is sinking in that Trump administration is on the precipice of turning into an establishment presidency," Sam Nunberg, a former Trump campaign adviser, said in an interview early Thursday morning.

While the initial wave of fury could change direction as new details emerge, the torrent represented the first major break of Trump's devoted base from the president on a core issue.

Rep. Steve King (R-Iowa), one of the GOP's biggest immigration hawks, issued a dramatic warning to the president after he scrolled through news reports.

"If AP is correct, Trump base is blown up, destroyed, irreparable, and disillusioned beyond repair," King tweeted, referencing an Associated Press story on the bipartisan agreement.

He added, "No promise is credible."

Conservative radio talk show host Laura Ingraham, who is friendly with Trump, mocked him for seeming to shelve the pledge that has animated his supporters since his campaign's launch.

Breitbart News, the conservative website now run by former White House chief strategist Stephen K. Bannon, quickly became a gathering place for aggrieved Trump backers. Readers congregated by the thousands in the comments section for an article with a bright red headline: "Amnesty Don."

Days earlier, Bannon said on CBS's "60 Minutes" that he was "worried about losing the House now because of this, because of DACA" â€” the Deferred Action for Childhood Arrivals program â€” arguing that Republican voters would lack enthusiasm for Trump and the party if they felt it was drifting to the center on immigration.

"If this goes all the way down to its logical conclusion, in February and March it will be a civil war inside the Republican Party that will be every bit as vitriolic as 2013," Bannon said, referencing the stalled fight that year over a comprehensive immigration bill. "And to me, doing that in the springboard of primary season for 2018 is extremely unwise."

"This a betrayal of the highest order," a Breitbart editor, who was not authorized to speak publicly, said in a phone call late Wednesday. "Donald Trump should be ashamed of himself. He wasn't elected to do this."

The editor was mostly echoed by the site's readers:

"Put a fork in Trump. He is done."

"PRIMARY TIME!!!!"

"What a HUGE let down."

"I can reconcile Trump caving on virtually any issue, Amnesty and not building the wall are not one of them."

Adding to the tumult in the deep of night: conflicting accounts over what exactly Trump and Democrats had brokered.

Aides to Senate Minority Leader Charles E. Schumer (D-N.Y.) and House Minority Leader Nancy Pelosi (D-Calif.) insisted that Trump had agreed not to request wall funding as part of their pact to soon move legislation to help undocumented immigrants who are protected by the Deferred Action for Childhood Arrivals program, an executive order established by President Obama in June 2012.

Others who have supported Trump's immigration positions took a wait-and-see approach amid the chaos.

"My sense is that he told Chuck and Nancy what they wanted to hear, and they heard what they wanted to hear. I think there could be some mischief-making on the part of Schumer since the White House is walking it back," said Mark Krikorian, an immigration hard-liner who runs the Center for Immigration Studies, in an interview.

Meanwhile, Fox News host Sean Hannity, who is in regular contact with Trump, directed his ire over the developments not at the president but at GOP leaders on Capitol Hill.